1. Field of the Invention
The present invention concerns an accurate and rapid system for assessing lachrymal fluid content in a person's eye and which also minimizes patient discomfort. More particularly, the invention concerns a sampling device for taking a representative lachrymal fluid sample from a person's eye, and an assessment device which determines an electrical parameter, preferably capacitance, which varies in accordance with the lachrymal fluid content of the sampling device and produces an output correlated therewith, such being thereby correlated with the lachrymal fluid content of the person's eye from which the sample was taken.
2. Description of the Prior Art
The lachrymal fluid content of a person's eye has a bearing on general eye health, and in particular, is a factor in whether a person can wear contact lenses. That is to say, if a person's eyes produce insufficient lachrymal fluid, that is tears, then contact lenses are contra-indicated because the potential for irritation and discomfort.
Those skilled in the art are familiar with the so-called Schirmer test for assessing the lachrymal fluid content of a person's eye. The Schirmer test developed in 1909, comprises an elongated, fluid absorbent sample member made of filter paper. One end of the member is inserted under the lower eye lid of the eye being checked with the other end protruding. The sample member is retained in the eye for five minutes in order to allow the member to absorb a sufficient sample amount. The distance the lachrymal fluid migrates or "wicks" along the member toward the exposed end is supposed to provide an indication of the lachrymal content of the person's eye. In reality, it performs more as a test of the eyes ability to produce lachrymal in response to the irritation and stress induced by the presence of the sample member.
As those skilled in the art will appreciate, the Schirmer test is not considered accurate because the relatively long term presence of the sampling member in a person's eye causes irritation and, in response, excess fluid production which distorts the results of the test. Because the test relies on wicking action, it also presents some inherent inaccuracies.